1. Technical Field
The present invention relates to a control device, an image display apparatus and a control method.
2. Related Art
In a state where an external device such as a DVD player and an image display apparatus such as a projector are connected with each other through a digital signal cable such as an HDMI cable, there is such a problem that no image is displayed, there is image flickering, noise is generated in a part of the image or the like, due to various causes. For example, such a problem occurs due to such a cause that the image display apparatus does not receive an image signal suitable for receiving performance of a receiving side, a copy protection function in the image display apparatus malfunctions, an image signal from the external device deteriorates in quality, the HDMI cable deteriorates in quality, or a receiving circuit of the image display apparatus does not have sufficient performance. For example, in JP-A-2007-140180, there is disclosed a projector which displays a user setting image regardless of a user's request, allows the user to set resolution or the like of the input image signal, updates setting data according to user setting information, and displays an image based on the image signal using the setting data, in a case where an image signal of which the type cannot be determined is input.
However, in the case of the method of displaying the user setting image regardless of the user's request, even though the type of the image signal may be appropriately determined, due to factors other than targets of a measuring section used for determining the signal type, for example, in a case where the image signal or the like cannot be normally received, there is such a problem that noise is generated in a part of the image, and thus, the image display apparatus may not display an appropriate image. Further, in the case of the method of displaying an image based on an input image signal and a user setting image to be overlapped, in a state where adjustment is not properly performed, the input image signal is in an unstable state and may or may not be normally received. Even though the input image signal is normally received, frequency of a sync signal becomes unstable, for example. Thus, the image display apparatus may not normally display even the user setting image, and a user may not adjust the user setting image. Further, for example, in a case where the HDMI cable is used, authentication according to HDCP (High-bandwidth Digital Content Protection) is performed. However, as the image display apparatus or the like performs the adjustment in a state where the authentication is successfully performed, an abnormal digital signal may be momentarily included in a signal which is a process target when an adjustment value is switched. Further, control or the like is performed on the basis of the abnormal signal, and thus, the image may not be appropriately displayed.